(1) Field of the Invention
The invention relates to a direct backlight module, and more particularly to a backlight module that can provide a backlight source to a liquid crystal display.
(2) Description of the Prior Art
With rapid development of thin film transistor (TFT) technology, especially in light weight, energy saving and non-radiation features, the liquid crystal display (LCD) has been widely used in various electronic devices such as personal digital assistants (PDA), notebook computers, digital cameras, slim televisions, mobile phones, and so on. In contrast to conventional cathode radiation devices, the liquid crystal display is benefited from a light source of a backlight module to make clear the information tossed to the display.
Referring to FIG. 1A and FIG. 1B, an exploded view of a typical LCD panel including a conventional direct backlight module and a cross-sectional view of the conventional direct backlight module are shown, respectively. As illustrated, the backlight module 1 located under an LCD 2 includes a base 10, a diffuser plate 11 and a plurality of films 12. In the base 10, a plurality of parallel lamps 13 are mounted. In the space formed between the lamps 13 and the interior bottom of the base 1, a common reflection plate 14 for reflection lights of the lamps 13 is included. The diffuser plate 11 located over the lamps 13 is typically a white light-permeable acrylic or polycarbonate plate to diffuse and so homogenize the lights provided by the lamps 13. The films 12 including multiple sheets and layered on the diffuser plate 11 are introduced to perform specific optical purposes. For example, the prism sheet is used to cluster lights, and the brightness-enhancement sheet is used to enhance the brightness of the LCD 2. Further, the films 12 can also have a diffuser sheet. In practice, the determination upon layers and sorts of the films 12 for a particular LCD panel is a designer option.
Ideally, the lights generated by the lamps 13 after passing the diffuser plate 11 and the films 12 are homogenized and thus can serve as a perfect backlight source to the LCD 2.
Also shown in FIG. 1A, the LCD 2 is mounted over the films 12 of the base 1. A bezel 3 is further mounted on top of the LCD 2 and engaged with the base 10 to complete the assembly of the LCD panel.
Nevertheless, the conventional direct backlight module 1 described above still has the following disadvantages.                a. The weight of the conventional backlight module is a negative factor to the LCD panel. As known, the diffuser plate in the art is usually made of acrylic, PC or glass material with a 2-4 mm thickness. Such a thickness will definitely become an awkward design as the dimension of the LCD panel becomes larger and larger.        b. The acrylic material of the diffuser plate is vulnerable to deform after a substantial period of exposure time under the lamps, from which the backlight quality is easy to be distorted.        c. The PC board for the diffuser plate will be gradually yellowed by the UV ray from the lamps, and thereby the backlight quality will definitely influenced.        d. The overall thickness of the direct backlight module including the diffuser plate and the lamps is too big to make the LCD panel slimmer.        
Therefore, a light-weight, thin and quality direct backlight module is always a topic to which the skill in the art is willing to devote.